During my masters in ocean engineering, I worked on a project to develop lidar for sea surface mapping. This is challenging because it breaks the assumptions that are made for terrestrial mapping.
While being used for mapping on land, like for autonomous driving, the scene is primarily static and filled with objects that are mostly opaque and produce diffuse reflections. Contrary to this, the sea surface is constantly changing and composed of water that is mostly translucent and produces specular reflections. Additionally, most commercially available lidar units use infrared lasers, which have very low reflectance for sea water.